Boss CE-2 troubleshooting

[znanjeiimanje]

Hello everyone, long time lurker but my first post on here.

I have a CE-2 that has started to drive me crazy. When it's plugged in and on, you do hear a slight change of the tonality vs the dry signal but not something you could call chorus. Basically there is no effect.

A couple of days ago I dismantled it and was about to change all the capacitors and left it open, some components touched each other and it started working, but with loud ticking. Since it was open on my workbench, when I moved it it stopped working.

I changed all the capacitors, nothing.

Re-confirmed all solder joints on the board, nothing.

Took out MN3001 and MN 3007, soldered them back in, nothing.

Then I got around to measure voltages across the board and all was fine except the TL022.

The readings I got were:

1 0
2 0.6
3 4.0
4 0
5 0.26
6 4.0
7 0.6
8 9.0

Where they should be:

1 VAR
2 4.5
3 VAR
4 0
5 4.5
6 4.5
7 VAR
8 9.0

I have tried swapping the TL022 to TL072 (the only one I could find) and it didn't change anything.

Anyone got any idea where I could continue looking as it doesn't seem to be the chip itself?

[CheapPedalCollector]

Voltages there are way wrong, usually indicating a bad op amp.

check VR3, R27 and R28 as well. Pull the chip and put in a socket so you can measure the voltages with the chip out of the circuit and see if VREF is 4.5v or so volts.

check Q1, Q2 and make sure they aren't blown/shorted, and Q3 to make sure it's working properly.

[znanjeiimanje]

Thanks a lot for the help.

I just checked and it's as follows:

- VR3 Seems to work fine and gives me 10k
- R27 and R28 I get 4.7k on both
- Q1, Q2, Q3 seem to be in order
- I pulled the chip and no way I can get 4.5 on the socket

Any other ideas would be appreciated.

[Kevin Mitchell]

I think the previous suggestion was to breadboard the opamp to test it.
Use two identical resistor values (like 2 10k resistors) between the power rails. That will give half of the supply voltage in-between them. Place that node on the + input of the opamp, short the - input to the output. This makes it a voltage reference buffer. So if you get 4.5v (half of a 9v supply) on the + input but something else on the output then you know the opamp is bad.

On the subject of what you did already, adjusting VR3 should allow you to dial in your voltage reference. Pin 3 of IC1 goes straight to that voltage reference and I see you wrote 4 volts, which appears normal. Though that voltage has nothing to do with determining if an opamp is bad or not. Extract and test externally.

Aaaaand welcome to the forum!!

[CheapPedalCollector]

OK, so check that you have ~9V at one end of R27, if you do then it's possible that C18 is shorted/out of spec. If you don't then start at D7, R52, C29 and C30. It's also possible Q9 is dead, try to avoid pulling parts unless you have to.

Also are you trying to run this on a power supply or battery. If power supply and it needs an ACA adapter you can do the voltage mod for it, or use a 12V supply. I suggest troubleshooting using a battery.

Troubleshooting is about isolating the problem by ruling things out. Also, use a magnifier check for bad solder joints and cracks in the traces.

[znanjeiimanje]

I think the previous suggestion was to breadboard the opamp to test it.
Use two identical resistor values (like 2 10k resistors) between the power rails. That will give half of the supply voltage in-between them. Place that node on the + input of the opamp, short the - input to the output. This makes it a voltage reference buffer. So if you get 4.5v (half of a 9v supply) on the + input but something else on the output then you know the opamp is bad.

On the subject of what you did already, adjusting VR3 should allow you to dial in your voltage reference. Pin 3 of IC1 goes straight to that voltage reference and I see you wrote 4 volts, which appears normal. Though that voltage has nothing to do with determining if an opamp is bad or not. Extract and test externally.

Aaaaand welcome to the forum!!

Thank you very much for the welcome. I did exactly what you wrote step by step and it appears normal. In addition I have swapped it with a new OP amp and all seems fine.

OK, so check that you have ~9V at one end of R27, if you do then it's possible that C18 is shorted/out of spec. If you don't then start at D7, R52, C29 and C30. It's also possible Q9 is dead, try to avoid pulling parts unless you have to.

Also are you trying to run this on a power supply or battery. If power supply and it needs an ACA adapter you can do the voltage mod for it, or use a 12V supply. I suggest troubleshooting using a battery.

Troubleshooting is about isolating the problem by ruling things out. Also, use a magnifier check for bad solder joints and cracks in the traces.

I started with the R27 and indeed I do have 8.9V at one end. I took out the C18 and replaced it with a new one, but I still get the same result. Seems like the issue could be before R27.

Also, I'm always running things on batteries so this time I can't blame the adapter.

[CheapPedalCollector]

OK then, measure Q9 in resistance mode of your meter. you should get 100ish ohms between Gate and Source, and more than a meg between Gate and Drain and also a couple megs between Source and Drain. Also check the diode connected to it.

[antonis]

It's always better to talk with a schematic availiable..

[Kevin Mitchell]

After reviewing this thread again;

To rule out Q9 you could just check for the wet signal before it. If it's there but not pin two of IC1 then you'd know that's the problem.

My first impression is either the LFO is locked up or BBD or driver is dead.

Check the LFO;
Turn the rate and depth fully CCW and probe the DC voltage going to pin 7 of the MN3101 and see if it's shifting. May be too fast to notice - in that case check the frequency there to see if there's anything going on.

Check the MN3101;
Use a multimeter to check the frequency on both pins 2 and 4 (I compare these to bike pedals, one goes high as the other goes low - effectively driving the two channels of the BBD)

Check the MN3007;
Make an audio probe and listen for pins 7/8 on the BBD. I'm guessing there's no sign of the guitar signal there. Doesn't mean it's bad though - unless the previous steps check out.

Best to test in that order to rule things out along the way.

[znanjeiimanje]

OK then, measure Q9 in resistance mode of your meter. you should get 100ish ohms between Gate and Source, and more than a meg between Gate and Drain and also a couple megs between Source and Drain. Also check the diode connected to it.

I tested it right now (in the circuit) and I get 340 ohms between Source and Gate, but I get nothing between Gate and Drain. Would this mean the transistor needs replacement?

After reviewing this thread again;

To rule out Q9 you could just check for the wet signal before it. If it's there but not pin two of IC1 then you'd know that's the problem.

My first impression is either the LFO is locked up or BBD or driver is dead.

Check the LFO;
Turn the rate and depth fully CCW and probe the DC voltage going to pin 7 of the MN3101 and see if it's shifting. May be too fast to notice - in that case check the frequency there to see if there's anything going on.

Check the MN3101;
Use a multimeter to check the frequency on both pins 2 and 4 (I compare these to bike pedals, one goes high as the other goes low - effectively driving the two channels of the BBD)

Check the MN3007;
Make an audio probe and listen for pins 7/8 on the BBD. I'm guessing there's no sign of the guitar signal there. Doesn't mean it's bad though - unless the previous steps check out.

Best to test in that order to rule things out along the way.

This I will try later tonight, I need to set up everything for the probe to work.

[CheapPedalCollector]

I was going off his first post where he said something shorted and it worked as intended, so I figured the clock and everything is functioning correctly.

If it's open entirely when testing Q9 between gate and drain and source and drain, probably the issue. It's a FET, usually SKY30A.

[Kevin Mitchell]

I was going off his first post where he said something shorted and it worked as intended, so I figured the clock and everything is functioning correctly.

Oops! Missed that 

Carry on 

[znanjeiimanje]

I was going off his first post where he said something shorted and it worked as intended, so I figured the clock and everything is functioning correctly.

If it's open entirely when testing Q9 between gate and drain and source and drain, probably the issue. It's a FET, usually SKY30A.

I just went around every electronic store near me and no one stocks 2SK30A. I also googled equivalents which turned out to be 2N5457 and NTE 458 but no one seems to stock those either.

Any idea what I could put instead of the original transistor in Q9?

[antonis]

2N3819, J105/6/7, BF256B, J111/2/3, 2N5484/5/6, 2SK369, 2SK371 etc..

[duck_arse]

2N3819, J105/6/7, BF256B, J111/2/3, 2N5484/5/6, 2SK369, 2SK371 etc..

CHECK  YOUR  PINOUTS whatever part you get.

[antonis]

2N3819, J105/6/7, BF256B, J111/2/3, 2N5484/5/6, 2SK369, 2SK371 etc..

CHECK  YOUR  PINOUTS whatever part you get.

ARE YOU TALKING (YELLING) TO ME..?? 

[Govmnt_Lacky]

I just went around every electronic store near me and no one stocks 2SK30A. I also googled equivalents which turned out to be 2N5457 and NTE 458 but no one seems to stock those either.

Any idea what I could put instead of the original transistor in Q9?

Did you check to see if you had a wet signal before Q9? Like at R22? Also, did you check to see if the wet signal is gone at Pin 2 of IC1? Answering this info would be helpful 

[duck_arse]

2N3819, J105/6/7, BF256B, J111/2/3, 2N5484/5/6, 2SK369, 2SK371 etc..

CHECK  YOUR  PINOUTS whatever part you get.

ARE YOU TALKING (YELLING) TO ME..?? 

if you have all those parts on your bench, I am emphasising, yes, not yelling.

[znanjeiimanje]

Thank you all for the help. The events meanwhile unfolded as follows:

2N3819, J105/6/7, BF256B, J111/2/3, 2N5484/5/6, 2SK369, 2SK371 etc..

CHECK  YOUR  PINOUTS whatever part you get.

Got a hold of BF256B, put it in, no difference. Still hear the dry signal and nothing else.

I just went around every electronic store near me and no one stocks 2SK30A. I also googled equivalents which turned out to be 2N5457 and NTE 458 but no one seems to stock those either.

Any idea what I could put instead of the original transistor in Q9?

Did you check to see if you had a wet signal before Q9? Like at R22? Also, did you check to see if the wet signal is gone at Pin 2 of IC1? Answering this info would be helpful 

I made a probe and there is no sound at R22 or at Pin 2 of IC1. Only place on IC1 where I hear a sound (quite distorted) is at Pin 6 of IC1.

After reviewing this thread again;

To rule out Q9 you could just check for the wet signal before it. If it's there but not pin two of IC1 then you'd know that's the problem.

My first impression is either the LFO is locked up or BBD or driver is dead.

Check the LFO;
Turn the rate and depth fully CCW and probe the DC voltage going to pin 7 of the MN3101 and see if it's shifting. May be too fast to notice - in that case check the frequency there to see if there's anything going on.

Check the MN3101;
Use a multimeter to check the frequency on both pins 2 and 4 (I compare these to bike pedals, one goes high as the other goes low - effectively driving the two channels of the BBD)

Check the MN3007;
Make an audio probe and listen for pins 7/8 on the BBD. I'm guessing there's no sign of the guitar signal there. Doesn't mean it's bad though - unless the previous steps check out.

Best to test in that order to rule things out along the way.

I did as stated above.

Point 1: at LFO the voltage isn't shifting at all and is fixed
Point 2: Could be my understanding as I am just starting to deal with pedals, but frequency on pin 1 vs pin 2 is a fixed 77, while vs pin 7 it's 100
Point 3: I hear no sound at all



Any other suggestions would be quite helpful

[Kevin Mitchell]

I made a probe and there is no sound at R22 or at Pin 2 of IC1. Only place on IC1 where I hear a sound (quite distorted) is at Pin 6 of IC1.

With no signal on R22 the wet signal isn't making it to the jfet.

Point 1: at LFO the voltage isn't shifting at all and is fixed

I should have said depth fully CW - that way you see a noticeable scoop in the voltage. But since you also checked frequency you know something is there. More in Point 2.

Point 2: Could be my understanding as I am just starting to deal with pedals, but frequency on pin 1 vs pin 2 is a fixed 77, while vs pin 7 it's 100

Put the depth fully CW and monitor the frequency of the LFO (pin 7 of the MN3101) as you increase the rate. Verify that it increases as you turn the rate up. Same thing with pins 2 & 4 which are what drives the MN3007. If you observe identical frequencies on pins 2 & 4 you know the clock is fine.

Point 3: I hear no sound at all

Prof that the clock isn't driving the BBD or the BBD is dead. Did you try adjusting VR3 as you audio probed the BBD's output? Moving forward; suspect the clock or LFO and check the frequency as you adjust the rate. Instructions in Point 2.
Could have blown something from the shorted connection mentioned in your first post. So it would be best to test these externally. If you have a breadboard I have a very simple circuit I use to quickly verify all of my BBDs & clocks. I'll post it if you think it'll be useful.

The thing is, none of us know exactly what's going on with your CE-2. But the fact that there's no signal coming from the BBD's output is THE place to focus on right now. Soldering and resoldering them is not wise. They should definitely be socketed.